Common VPN Server Issues

A VPN is actually one of the most technically sophisticated network security solutions. However, if you think that the implementation of a VPN would solve all of your security-related issues, then you are probably mistaken. Attacking technology has advanced by leaps and bounds. This article discusses some of the most common VPN server issues encountered by users.

VPN Server Issues

VPN server issues typically fall under the following categories:

The VPN connection attempt is rejected.

Unauthorized VPN connection is accepted.

Inability to reach locations further to the VPN server.

Inability to establish a tunnel.

The VPN connection attempt is rejected: Having a VPN connection attempt rejected is one of the most common VPN server issues. A lot of issues can contribute to this rejection. Here are some troubleshooting tips that you can use to resolve this issue:

Check if the Remote and Routing Access service is operating on the VPN server.

If you have a remote access VPN connection, check if the VPN server has been enabled for remote access.

Check if the IP address or host name of the VPN server is reachable, by using the Ping command.

Make sure that all of the L2TP or PPTP ports of the VPN server are not being used already. You can change the number of PPTP to L2TP ports to enable more concurrent connections.

Unauthorized VPN connection is accepted: Now that we have discussed some common reasons that may lead to the rejection of your VPN connection, let us now see why unauthorized connections are accepted. VPN server issues of this type can lead to security issues.

Check that the connection’s parameters do not have authorization via remote access policies. The Deny Remote Access permission must be selected in order to deny the attempt to achieve a VPN connection.

Inability to reach locations further to the VPN server: Following are some reasons why you may be unable to reach locations further to the VPN server:

In case of remote access VPNs, make sure that the protocol for routing is enabled or the Entire Network option has to be selected for you to use the LAN protocols.

For router-to-router VPN connections that are one-way initiated, check on the dial-in properties whether the calling router’s intranet routes are configured as static.

Also, ensure that routes are available on both sides of the router-to-router VPN connection. This helps in supporting the two-way exchange of traffic.

Inability to establish a tunnel: If all the above mentioned options seem to work properly, but you are unable to establish a tunnel with the server, there might be two possible reasons.

The packet filtering on a router interface might be prevent the forwarding of tunneling protocol traffic, or

There might be a proxy server between the VPN client and the VPN server.